The mechanical textile recycling process significantly reduces fibre length. Previously, we explored how lubricant pre-treatment before mechanical recycling reduced the fibre length loss. In this study, we added simulated wear to assess its influence on the fibre length output. We also evaluated the influence of sample shape and feed direction on recycling efficiency. We treated plain woven cotton textiles were subjected to either sandpaper grinding or steel needle raising. Finishing treatments with polyethylene glycol 4000 and Afilan CFA 100 were also used in combination. Samples were prepared in two shapes and fed into the recycling machine with warp threads oriented longitudinally, perpendicularly, or diagonally. Recycling efficiency was evaluated based on fibre length and the degree of fibre opening using a novel air flow permeability test. The results showed that sandpaper treatment degraded fibres, while the raising treatment improved recycling efficiency. A previously unreported finding was that the size, shape and feeding direction of woven fabrics showed significant effects on the fibre length output. Material fed with a thread system aligned longitudinally to the recycling machine direction resulted in a higher proportion of opened fibres and fewer unopened fabric pieces. It was further observed that the yarns aligned longitudinally with the feed direction exhibited significant opening, while those oriented perpendicularly remained largely unopened. The new method for measuring the degree of opened fibres proved effective and holds promise for future application. These findings provide tangible guidance on the mechanical recycling protocol and means to improve output assessment procedures.

Several qualities influence the processability of textile staple fibers: inter-fiber cohesion being one of the most important properties. Although various methods to measure this property have been explored, there is no consensus on the optimal technique, and existing methods often require specialized machinery. This article introduces and evaluates a straightforward method that utilizes only a carding machine and a tensile tester, both standard equipment in yarn laboratories. The proposed cohesion test method involves preparing carded webs, cutting them into nine rectangles, and then subjecting these samples to tensile testing. The method was initially assessed for repeatability and the normalization of results. Further experiments varied the fiber material (cotton and polyester), fiber organization, direction of fiber hooks, and finishing treatments. Force curves and their gradients were analyzed, alongside video footage, to study inter-fiber interactions during testing. The results demonstrated that the new test method could differentiate between fiber materials, fiber organizations, and quantify the effects from finishing treatments. The cohesion force (CF) of CO fibers was 30% of that of PES fibers; carding had a greater impact on CO fibers compared to PES fibers, and treatment with lubricant reduced the CF by up to 35%. However, the weight and dimensions of the samples must be controlled to ensure repeatability. In conclusion, the developed inter-fiber cohesion test method offers a promising and accessible approach to analyzing inter-fiber interactions in staple fibers.

Although there has been some research on how to use short fibers from mechanically recycled textiles, little is known about how to preserve the length of recycled fibers, and thus maintain their properties. The aim of this study is to investigate whether a pre-treatment with lubricant could mitigate fiber length reduction from tearing. This could facilitate the spinning of a 100% recycled yarn. Additionally, this study set out to develop a new test method to assess the effect of lubricant loading. Inter-fiber cohesion was measured in a tensile tester on carded fiber webs. We used polyethylene glycol (PEG) 4000 aqueous solution as a lubricant to treat fibers and woven fabrics of cotton, polyester (PES), and cotton/polyester. Measurements of fiber length and percentage of unopened material showed the harshness and efficiency of the tearing process. Treatment with PEG 4000 decreased inter-fiber cohesion, reduced fiber length loss, and facilitated a more efficient tearing process, especially for PES. The study showed that treating fabric with PEG enabled rotor spinning of 100% recycled fibers. The inter-fiber cohesion test method suggested appropriate lubricant loadings, which were shown to mitigate tearing harshness and facilitate fabric disintegration in recycling.

The demand for textile fibres is growing quickly. However, global cotton production has stabilized around 25 Mton/year. This is a sound development since cotton cultivation causes major sustainable development issues. Even if regenerated cellulose fibre production steadily grows, it is still only from a sixth to a fifth of cotton volumes. Hence, it is essential to find resource-efficient routes to generate alternatives to virgin cotton. There are many promising research initiatives that discover the possibility to utilize waste streams of neat cotton and cotton in fibre blends as raw materials for dissolving pulp for regeneration into, for example, viscose or Lyocell. However, there is a much simpler and energy-efficient route at hand. If fabrics are disintegrated mechanically, the separated fibres can be turned into yarn again. However, since fibre length is a key parameter to accomplish strong and durable textiles, fibre length loss upon tearing should be minimized. This study evaluates how fibre length distribution alters upon tearing of post-consumer cotton waste of two different constructions: denim and single jersey; and different degrees of wear, rendering four different fractions: (1) barely worn denim, (2) rather worn denim, (3) barely worn single-jersey and (4) rather worn single-jersey. Before tearing, the garments were dissembled, their yarns were characterized, fibre length distributions were manually determined for (1)–(4). Length analysis of the recovered fibres after tearing revealed that the length drop was most severe for (a) the finer single-jersey and (b) the barely worn fractions. The findings suggest that significant wear does not exclude from mechanical recycling.

To decrease the environmental burden of the textile industry and at the same time reduce textile waste, the fibers of discarded textiles can be re-used into new yarns and fabrics. The shortening of fibers during mechanical shredding direct the use of the recovered fibers to low value products. With the use of a lubricant pre-treatment on cotton and polyester fabrics, we decreased the friction during shredding. The reduction in friction was shown with a developed inter-fiber friction test. Further, the pre-treatment was shown to give longer recovered fibers and eliminate melted areas in polyester material.

Cotton is not the answer to meet the rapidly growing demand for textile fibers. Wood-based regenerated cellulose fibers are an attractive alternative. Since wood is a candidate to replace fossil raw materials in so many applications of the circular economy, other sources need investigation. Cotton linters work in the viscose process – can cotton waste be used to make dissolving pulp? We describe the textile qualities of lyocell fibers from (i) pure cotton waste pulp and (ii) blending with conventional dissolving pulp. The staple fibers were tensile tested, yarns spun and tensile tested and knitted, and tested for shrinkage, water and dye sorption, abrasion resistance, fuzzing and pilling, staining and fastness. TENCEL® staple fibers and off-the-shelf TENCEL® yarn were used as references. The results show that the two study fibers had tenacity and an E-modulus that exceeded the staple fiber reference. Also, the study yarns were at least as good as the spun reference yarn and the commercial off-the-shelf yarn in terms of wet tenacity. Single jerseys made from the study yarns shrunk less upon laundering, which is surprising since they could absorb at least as much water at a comparable rate as the references. Dyeability, staining and color fastness, durability and pilling tendency showed that the two study fiber tricots performed at least as good as the references. This study suggests that cotton waste is a promising candidate for special grade pulp to suit niche regenerated fiber products or to spice up conventional wood-based dissolving pulp.

Ioncell-F, a recently developed process for the production of man-made cellulosic fibers from ionic liquid solutions by dry-jet wet spinning, is presented as an alternative to the viscose and N-methylmorpholine N-oxide (NMMO)-based Lyocell processes. The ionic liquid 1,5-diazabicyclo[4.3.0]non-5-ene acetate was identified as excellent cellulose solvent allowing for a rapid dissolution at moderate temperatures and subsequent shaping into continuous filaments. The highly oriented cellulose fibers obtained upon coagulation in cold water exhibited superior tenacity, exceeding that of commercial viscose and NMMO-based Lyocell (Tencel®) fibers. The respective staple fibers, which have been converted into two-ply yarn by ring spinning technology, presented very high tenacity. Furthermore, the Ioncell yarn showed very good behavior during the knitting and weaving processes, reflecting the quality of the produced yarn. The successfully knitted and woven garments from the Ioncell yarn demonstrate the suitability of this particular ionic liquid for the production of man-made cellulosic fibers and thus give a promising outlook for the future of the Ioncell-F process.

Natural fibers today are a popular choice for applications in composite manufacturing. Based on the sustainability benefits, biofibers such as plant fibers are replacing synthetic fibers in composites. These fibers are used to manufacture several biocomposites. The chemical composition and properties of each of the fibers changes, which demands the detailed comparison of these fibers. The reinforcement potential of natural fibers and their properties have been described in numerous papers. Today, high performance biocomposites are produced from several years of research. Plant fibers, particularly bast and leaf, find applications in automotive industries. While most of the other fibers are explored in lab scales they have not yet found large-scale commercial applications. It is necessary to also consider other fibers such as ones made from seed (coir) and animals (chicken feather) as they are secondary or made from waste products. Few plant fibers such as bast fibers are often reviewed briefly but other plant and animal fibers are not discussed in detail. This review paper discusses all the six types of plant fibers such as bast, leaf, seed, straw, grass, and wood, together with animal fibers and regenerated cellulose fibers. Additionally, the review considers developments dealing with natural fibers and their composites. The fiber source, extraction, availability, type, composition, and mechanical properties are discussed. The advantages and disadvantages of using each biofiber are discussed. Three fabric architectures such as nonwoven, woven and knitted have been briefly discussed. Finally, the paper presents the overview of the results from the composites made from each fiber with suitable references for in-depth studies.

ABSTRACTPolyester (PET) has wide applications in textile industries as textile fiber and its share continues to grow. Substantial quantities of cotton/polyester blend fabrics are disposed every year due to technical challenges, which pose a big environmental and waste‐dumping problem. The aim of this study is to evaluate the potential of discarded cotton/PET fabrics as raw materials for composites. If their inherent reinforcement properties can be used in composites, an ecological footprint issue can be solved. In this study, we investigate three concepts for reuse of cotton/PET fabrics for composites: compression molding above the Tm of PETs, use of a matrix derived from renewable soybean oil, use of thermoplastic copolyester/polyester bi‐component fibers as matrix. All three concepts have been explored to make them available for wider applications. The effects of processing parameters such as compression temperature, time and pressure are considered in all three cases. The third concept gives the most appealing properties, which combine good tensile properties with toughness; more than four times better tensile strength than the first concept; and 2.2 times better than the second concept. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40687.

The distribution of aluminium borate whiskers in blends of polyethylene/polyisobutylene (PE/PIB) was studied with respect to viscosities of the components. Both polymers are non-polar with slightly higher surface energy for the PE, i.e. weak filler–polymer interactions of about equal strength. The significance of the polymers' viscosity disparity can thus be studied in isolation. Two PEs and two PIBs with clearly separated flow curves (ηPE1>ηPIB1≫ηPE2>ηPIB2) were used. The whiskers were found in the high viscosity phase except when they promoted coherency of the low viscosity minority phase. However, the PE's slightly higher surface energy ruled the absorption although PIB was slightly more viscous showing the relative weakness of this rheological phenomenon. Furthermore, the viscosity distributing factor was found to be less important than polar interactions. A rheological explanation is presented that supports the observed selective absorption.

The rheological time dependencies of both whisker-filled (composites) and unfilled PE/PIB and SAN/PA6 blends were studied as functions of composition and shear history. A three-step experiment of steady dynamic—steady shear was designed. Rupture and formation of the morphology in batch-compounded blends/composites was conveniently and accurately studied in the first steady shear. The second step emphasises morphological sensitivity in blends close to phase inversion. During the oscillation phase metamorphosis and whisker transport were noticed. The third step together with microscopy studies confirmed these observations.

The morphology of a polymer blend can be altered very dramatically when a filler is added. Depending on the mutual interactions of the polymers and their individual interactions with the filler, many different filler distributions are possible. Inverse gas chromatography was the key tool to quantify the polymer-solid interaction potentials in terms of Lewis acid-base properties. These forecasted interaction strengths at the whisker-polymer interface coincided with the observed preferential adsorption. Selective adsorption of the minority polymer component made it form three-dimensional web structures with the whiskers in the matrix of the majority component. This ability to form co-continuous structures was quantified as electrical conductivity of blends containing the intrinsically conducting polymer poly(3-octyl thiophene). For a properly selected majority polymer the conductivity of the three-component composite increased several orders of magnitude. Interactions between polyamide-6 and the whisker surface are strong enough to perturb crystallization in a zone by the interface. Selective adsorption was exploited to create virtually highly filled composites as a non-interacting polymer was added as a processing aid. That polymer was extracted and left extreme composites comprising only whiskers and polamide-6 interphase. In order to collect data for derivation of a crystallinity gradient by the filler surface, the ratio of polyamide-6 to processing aid was varied. Once a beneficial phase morphology has been achieved, successive processing can easily rupture it unless its rheological limitations are considered. For example, the high shear rates created during injection molding ruined the co-continuous structure created during compounding of poly(styrene-co-acrylonitrile)/polyamide-6/whiskers. However, the ruptured morphology could have been restored by annealing at the processing temperature. In blends with components of comparable polymer-whisker interaction strength and substantial viscosity difference the whiskers are absorbed by the phase that minimizes the viscosity of the three-component system. Accordingly the whiskers were absorbed by the high viscosity phase unless supporting transformation of the minority low viscosity phase from dispersed to continuous. Such transformations and other shear induced morphological changes were followed as viscoelastic changes during steady and/or harmonic shear. This methodology has the prospects to become a valid instrument to optimize the processing route of blends and multicomponent systems.

The influence of aluminum borate whiskers upon the morphology of polyamide 6 was studied by wide-angle X-ray scattering and by differential scanning calorimetry. The whiskers did not promote the formation of either the hexagonal gamma or the monoclinic beta crystalline phase. A new experimental procedure has been devised for the production of very thin polymer layers on the whiskers. In the procedure, styrene coacrylonitrile polymer is used as a processing aid and is later extracted. The procedure allows for the generation of polyamide layers less than 30 nm thick. Crystallinity in these thin layers was suppressed. An expression has been developed to characterize the crystallinity gradient in the interphase of the whisker surface. The equation shows that the initial 1.4 nm of polymer is fully amorphous and produces excellent evaluations of the crystallinity gradient to layer thicknesses of 70 nm. (C) 1997 John Wiley & Sons, Inc.

The influence of a filler on melt-mixed conducting polymer blends of poly(3-octylthiophene) (POT) has been examined with respect to their morphology, rheology, conductivity and acid-base properties. The matrix polymers used were low density polyethylene (LDPE), poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) and the filler was non-conducting aluminum borate whiskers. These blends show two-phase behavior when examined by scanning electron microscopy. It was found that the adhesion at the polymer-filler interface in combination with the viscosity ratios between the polymers exerts a considerable influence on the morphology and hence on the conductivity. For the PE/POT blends, addition of whiskers changed the morphology and increased the conductivity by several orders of magnitude. The conductivity of blends with PVC was almost unchanged while the conductivity of PMMA blends slightly decreased upon addition of whiskers. The interactions between whiskers and the polymers used decreased in the order: PMMA > POT > PVC > PE. This is in accordance with the Lewis acid-base properties determined by inverse gas chromatography.

The effects of aluminum borate whiskers on melt mixed poly(styrene-co-acrylonitrile)/polyamide 6 (SAN-PA6) blends have been investigated. With SAN as the major component, scanning electron microscopy reveals that PA6 creates a continuous phase with the whiskers, i.e a co-continuous morphology is created. For the inverse system, with PA6 as the major component, this effect does not occur. The interactions between PA6-whiskers and SAN-whiskers have been quantified as Lewis acid-base properties using inverse gas chromatography (IGC) at infinite dilution. Interactions between whiskers in PA6 are much stronger than between whiskers in SAN. The morphology of blends with SAN as the majority component is not stable at high shear rates. This can be explained by the rheological characteristics of the components, i.e. a crossover point in viscosity as a function of shear rate.